The purpose of the project is to clarify the relationship between structure and antitumor activity in the antinomycin series. This includes structure determination of some novel actinomycins and a study of the secondary structure (conformation) of various actinomycins by NMR techniques. Also comparative physicochemical studies of different actinomycins in complexation with nucleotides will be undertaken. Actinomycin D has limited usefulness as an antineoplastic drug. Many structural variations are known but have not been adequately tested to ascertain whether a superior alternative to D exists. The present work is bringing new structures forwarded and in clarifying structure-activity relationships may identify likely candidates for further evaluation.